OAKLAND, Calif. (KTVU) - A wildfire burning in Yolo County more than doubled in size Sunday as fire crews battling it, dealt with triple-digit heat.

The “County Fire,” as it’s being called, started Saturday afternoon near Lake Berryessa and spread quickly. By Sunday, it was already bigger than the Pawnee Fire, which continues to burn in Lake County, and the flames crossed the line into Napa County.

With temperatures well above the one-hundred degree mark, fire crews relied on aircraft, including at least 12 helicopters, to make repeated drops of water on the fire.

“The fire runs uphill much quicker than we can and with the men and women in all that heavy gear, it’s just too dangerous to be in some of those areas,” Craig Doppmann of Cal Fire explained.

Mandatory evacuations are now in effect north of Highway 128 and south of County Road 23. An evacuation center has been set up in the town of Guinda but on Sunday afternoon there was no one there.

Natalie and Paul Klempau own the Taber Ranch Vineyard and Event Center which is under a voluntary evacuation order. They both were unsettled by the sight of a large plume of smoke coming over the ridge.

“This is our livelihood and we put our blood, sweat and tears into this place,” Paul Klempau said. “So we don’t want to see it go up in flames.”